i BO CONG THU'ONG TONG CONG TY TB DIBN VIETNAM CONG TY CP Kill CU DIEN I CONG HOA XA HOI CHU NGHIA VIET NAM Doc lap - Tu do - Hanh phuc San tdy. ngdy 03 tJiang 11 ndm2009 BAO CAO THUYET MINH DE TAX I<HOA HOC VA CONG NGHE CAP BO .X, Nghien cuu, thiet ke va hoan thien thiet bj, cong nghe che tao Balat 2 cap cong suat 150 W/100 W, Bo chuyen doi cong suSt va Bo khoi dgng dCing cho den Natri cao ap Chii nhiem de tai: Co" quan thu-c hien dc tai: Co' quan chii quan de tai: Nguyen Luong Tung - Ky sir co khi Cong ty Co phan Khi cu dien 1. Bo Cong Thuang Chii nhiem dc tai Don vi thuc hien ;GIAM Ks.Nguyen Luong Tung ^,^ sw. •«^« i^-^fV W't 1112 -766/1 MUC LUC Trang Ldi noi ddu 5 Phdn 1. Nguyen ly hoat dong den HPS 2 cap cong suat 9 Phdn 11. Thiet ke che tao Balat 2 cAp cong suSt 150 W/lOO W - 220 V 13 II. 1. Trien khai thiet ke ^ ^ II. 1.1. Cac chiing loai balat cho den phong dien cuang do cao 13 II. 1.2. Ca sa thiet ke, tinh toan balat sat tircho den Natri cao ap .' 14 1. Ca sa ly thuyet 14 2. Thong so, cong thiic tinh caban 14 II.1.3. Tinh toan thiet kg 17 A. Tinh toan sa bo '. 17 B. Tinh toan kiem tra '. 19 II.1.4 Thia kl chi tilt chi tao 26 II.2. Trien khai thiet ke va che tao khuon mau 29 11.2.1. Khuon ep cac chi tiet nliua 29 11.2.2. Khuon dap cat dot cac chi tiet kim loai 30 Phdn 111. Thiet ke bo chuyen doi cong suat 32 111.1. Phan tich nguyen ly hoat dong lira chon phuang an thiet ke 32 111.2. Thiet ke ra le thai gian 2 miic 4h - 5h theo phuong an tao dao dong diing dien tra va tu dien (R-C) 32 111.2.1. Lira chgn linh kien chinh 32 111.2.2. Cac chi tieu thiet kl 33 111.2.3. Sa do mach dien ra le thai gian 2 che do 4h - 5h 33 111.2.4. Lua chon linh kien phu 33 111.3. Xay dung quy trinh cong nghe 41 III.4 Trien khai thiet ke va che tao khuon nhua 42 Phdn IV. Thiet ke bo khoi dong :.43 IV.1. Tong quan ve bo khai dong den (IGNITOR) 43 IV.2. Phan tich nguyen ly hoat dong, lira chon phuang an thiet ke 43 IV.3. Tinh toan lira chpn cac gia trj linh kien 45 IV.4. Thiet ke mach in va vo 48 3/72 IV.5. Xay dung quy trinh cong nghe 50 IV.6. Trien khai thiet ke va che tao khuon nhua 50 PJu'm V: Gia cong chi tiet va 15p rap 51 V.l. Gia cong chi tiet 51 V.1.1. Gia cong chi tiet nhua 51 V.1.2. Gia cong chi tiet kim loai 54 V.2. Lap rap 55 V.2.1 Lap rap balat 55 V.2.2 Lap rap bo chuyen doi cong suit 58 V.2.3 Lap rap bo khai dong 59 Phdn VI: Thii'nghiem va hieu chinh 60 VI.1. Balat 2 cap cong suat 60 VI.2. Bo chuyen doi cong suat. 61 VI.3. Bo khai dong 64 Phdn VII: Ket qua dat duo'c 65 VII.l. Hinh dang ngoai quan 65 VII.2. Chat lugng san pham 66 Phdn VIII: Phu luc 67 4/72 LOINOIDAU The giai ciia chiing ta hien nay dang bi 6 nhiem, tai nguyen thien nhien dang bi khai thac den can kiet, sii dung nang lugng qua miic gay hieu ung nha kinh dang lam trai dat nong dan len gay ra muc nuoc bien dang cao va bien doi Idiac thuong ve ki^i • dan den tham hoa thien nhien va moi truang. Lien hgp quoc ciing cac quoc gia thanh vien da va dang dua ra nhiing chuang trinh cu the nham cim van tinh hinh tren. Mot trong nhUng chuong trinh do la chuang trinh tiet kiem nang lugng toan cau. Nhieu giai phap thiet thuc da dugc dua ra, trong do la tao san pham cong nghiep cung nhu dan dung tieu hao it nhien lieu va nang lugng hon. Cong ty CO phan Khi cu dien I khong che tao ra cac san i^ham tieu thu dien nang, cac san pham ciia Cong ty chu yeu la thiet bi dong cat va thiet bi ho trg trong chieu sang. Mac dii vay cac san pham tren ciia Cong ty quyet dinli dang ke den hieu suat sir dung thiet bi tieu thu nang lugng. Ban than san pham ciia Conj.' ty trong qua trinh tham gia hoat dong ciing tieu thu mot lugng nang lugng rieng nho. Nhan thirc dugc tam quan trong tren, trong tinh toan thiet ke va che tao Cong ty ciing chu trong den nhung bien phap de tang hieu qua ciia thiet bi tieu thu dien, dong thoi giam thieu toi da mirc tieu thu rieng. Trong cac san pham cua Cong ty, dac biet la cac loai Balat cho den huynh quang, balat cho den Natri cao ap Cong ty de cao den hieu qua ciia tiet kiem nang lugng. Nam 2007 Cong ty don nhan 02 san pham dugc dc.n nhan tiet kiem dien do Bo Cong Thuong trao; 1. Balat sat tir 40 W/220 V dimg cho den TIO & T8 2. Balat sat tir 20 W/220 V diing cho denTlO & T8 Tiep tuc cong viec phan khai do, Cong ty VINAKIP trien khai bo dieu khien 2 muc cho den Natri cao ap (HPS) trong chieu sang cong cong hieu suat cao. Hien trang viec sir dung den Natri cao ap tai cac do ihi ciia nuoc ta hien nay: He thong chieu sang cong cong tai cac do thi hien nay phan Ion da dugc thay the tir den thuy ngan cao ap sang den Natri cao ap mot mirc cong suat. Thai gian chieu sang thong thuang la 11 gia moi dem. Trong thai gian tir 0 gia den 6 gia sang hom sau cong suat den tang tir 108 %P den 110 %P do dien ap tang cao hon dinh mirc lam tang dang ke cong suat ciia bong den trong khi do nhu cau chieu sang lai giam. De giai quyet tinh trang nay nganh chieu sang cong cong dua ra nhieu giai p'aap thiet thuc nliam giam bat mirc tieu thu dien: 5/72 * Cat bat chieu sang : Sir dung che do chieu sang ngat quang (diing 1 den va cat bo 1 den). Bien phap nay de thuc thi, tiet kiem 50% nang lugng chieu sang, song co nhieu bat cap: Mat do chieu sang khong deu, khong dam bao an toan giao thong va an ninh duang pho. * Giam bat dien ap sau giof cao diem: Sau giof cao diem dien ap chieu sang thuang bang hoac qua dien ap dinh miic (> 220 V). Nguai ta diing thiet bi dieu chinh dien ap dua dien luai bang hoac lan hon 92% dien ap dinh miic chiit it va khong nhn hon dien ap khai dgng ciia den (>202,4 V). Vai giai phap nay co the tiet kiem dugc den 20 % lugng dien tieu thu. Nhugc diem la dau tu ton kem, va can phai bao dudng them thilt bi * Sir dung he thong chieu sang trung tam: Sir dung trung tam dieu khien he thong chieu sang bang he thong mang : He thong nay rat hien dai, doi hoi cong nghe cao, dau tu Ion. He thong cung cap anh sang theo thai gian, thai tiet va theo miia. He thing dieu khien anh sang lien tuc theo timg gia nhu cau va theo tirng kliu vuc. De quan ly theo each thiic hien dai, khi dua trung tam vao hoat dong, he thong se tu dong dieu chinh dien ap cho timg bong den tren khap dia ban. Dieu do vira co tac dung giam dien nang tieu thu cho he thong chieu sang cong cong, vira tang tuoi tho cho timg bong den, giiip tilt kiem diu tu thay the bong. Mat khac, trung tam cung se thong ke, luu tru: dac diem chi tiet cua tirng thiet bj, timg bong den, qua do giiip chiing ta nam dugc ly lich timg den de quan ly va thay the cac vat tu, thiet bi het thai han sir dung, giup tang hieu qua quan ly. * Sir dung bo dieu khien 2 cap cong suat, day la giai phap cue bo, moi mot den sau 11 hoac 12 gia dem, tu giam cong suat nha co balat 2 cap cong suat va bo chuyen dii cong suit. Bo dieu khien 2 cap cong suat cung giong nliu dieu khien 1 cap, thay the ballat 1 cip cong suit bing balat 2 cap vai bo chuyen doi cong suat tu dong dat gia. Phuang an nay dan gian de lip dat, dau tu khong ton kem, khong can dong bg, hieu qua tilt kiem cao giam 30 % den 40 % dien tieu thu khi chuyen doi cong suat. Hien nay c6 nhilu nuac trien khai chS tao va sir dung balat 2 cap vai mirc cong suat 150 W/100 W, 250 W/150 W va 400 W/250 W. 6/72 Tinh uu vi^t khi sv dung bo Balat hai cap cong suat: 1. Tiet kiem dien nang tieu thu 110% 100% 19 P 4 7 h 24h ,,^„^^„ Hinh 1: Bieu do tieu th 6 u dien nar * 5 h dau cong suat dat 92 %P do dien ap sut (8-10) % (gia cao diem ciia cac phu tai tieu thu) * 6 h sau cong suat tang tir 108 %P - 110 %P do dien ap luai dien tang cao han dien ap T(gi dinh muc tl) [1 * ; (tir Oh den 6h sang) Cong suat dac trung tieu thu cua moi dem ig ciia balat mot cap cong suat Tir do thi hinh 1 ta c6 the tinh cong suat tieu thu cua den 150W: Vai 5 h chieu sang dau tien, tong cong suat sir dung ciia balat 150 W la: 5hxl50Wx92% = 690W Vai 6 h chieu sang tiep theo, toi da cong suat sir dung cua balat 150 W la: 6hxl50WxllO% = 990W T6ng cong suit su dung trong mot nam cua balat 150 W thong thuang la: (690 W + 990 W) X 365 ngay = 613.200 W = 613,2 kW 110% 100% 92% 60% ^ Ghi chu: ••; ^ [/ ^ ^r /; C.^ Z ^ ^ :/ k y/ hi lap Cong suat tiet kiem dat thiet bi dieu khien cong suat giam khoang 25 % tl leo SC II 1 do ben. Cong suat su dung chieu sang cong cong trong mot dem. T(g 9h 24h ._ .6h io-) Hinh 2: Bieu dd tieu thu dien nang cua balat hai cap cong suit 7/72 > r f ' m ' Tir do thi Hinh 2 ta thay, viing vach mau do ( ) bieu thi cong suat sur dung chieu sang, ciing nhu viing hoat dgng ciia balat 1 cap cong suat 150 W thong thuang. Viing vach mau xanh ( ) bieu thi cong suat tiet kiem dugc khi su dung balat 2 cap cong suat 150 W/100 W. Vai balat 2 cap cong suat, tong cong suit su dung cho chieu sang trong 1 nam nhu sau: - Vai 5 h chieu sang dau tien, tong cong suat su dung cua balat 2 muc cong suat 150 W/100 W la: 5 h X 150 W X 92% = 690 W. - Vai 6 h chieu sang tiep theo, tinh nang ciia balat 2 cap cong suit dugc phat huy, khi do t6ng cong suit sii dung la: 6 h x 100 W x 110 % = 660 W. Tong cong suat su dung trong mot nam ciia balat 2 cap cong suat 150 W/100 W la: (690 W + 660 W) X 365 ngay = 492.75 W = 492,75 kW tilt kiem han so vai loai balat 1 cip cong suit 150 W la: 613,2kW - 492,75 kW = 120,45 kW. 2. Cuang do anh sang luon dugc phan bo dong deu. 3. Tang cuang tu6i thg cho thiet bi chieu sang (day dan,b6ng den, Balat) 4. Giam 6 nhilm moi truang, phat thai khi de tao ra lugng dien nang tiet kiem dugc. Vdi lai ich cua ba lat 2 cap cong suat, xet ve nang luc che tao tai cong ty. Ban lanh dao quyit dinh triin khai thih kk & chi tao ba lat 2 cdp cong sudt 150 W/100 W, tren car sd da chi tao ba lat 1 cdp cong sudt, Bg chuyin ddi cong sudt cung hgrp tdc vdi vien Ndng luffng thuoc vien Khoa hgc vd Cong nghe Viet nam thiit ki chi tao, Bg khdi dgng se do phong R&D nghien ciru thiit ki vd chi tao tai cdng ty, todn bg cong viec tren dang ky lam di tai cdp Bg ndm 2009. Trong khuon kho dl tai chiing toi xin trinh bay cac hang muc cong viec sau: Phin 1: Nguyen ly hoat dgng ciia den 2 cap cong suat Phin 2: Thilt kl chi tao balat 2 cap cong suat Phin 3: Thilt kl chi tao bg chuyin ddi cong suat Phin 4: Thilt kl che tao bg khai dgng Phin 5: Gia cong chi tilt va lap rap Phin 6: Thu nghiem va hieu chinh Phin 7: Kit qua dat dugc. Phin 8: Phu luc (Cac van ban, ho sa giay ta kem theo). 8/72 PHANI NGUYEN LY HOAT DONG CUA DEN HPS 2 CAP CONG SUAT 1. So do nguyen ly chung: Balat P1/P2 * Den Pl la den co cong suat dinh mirc PI (W) tuong ung vai Balat hai cap cong suat vai mirc cong suat cao nliat la PI (W). * Bg khai dgng chi lam viec khi bat dau cap dien, luc do dien ap rai tren 2 cue cua den tir 2,8kV den 5kV gay phong dien. * Balat 2 cap cong suat ban chat la balat lam viec a che do dinh miic co dau noi tiep them cugn kliang phu, co the lam viec dugc 2 che do tren cimg 1 bong den. * Bg chuyen doi cho phep dong dien di qua tuang duang vai dong khai dgng Ion nhat cua den, dong se giam dan va on dinh khi tra ve hoat dgng a dinh muc. * Lap them tu bii nham tang he so cong suat. 9/72 2. Nguyen ly hoat dong ciia den HPS 150W/220V Cong suat den lan nhat 180 > a •J 3 v> m c <o O 150 105 Dien ap den nho nhat Cong suat den nho nhat u II ; Dien ap den 1 Ion nhat Dac tinh Balat 73 100 103 113 170 Dien ap tren den (V) • Balat nhu cugn khang co nhiem vu dat dien ap len den lOOV, den se tieu thu 150 W (cong suat dinh mirc ciia den). Klii chuyen sang cong suat thap, tong tra khang (cuon khang chinh va phu) ciia balat dat dien ap tren den khoang 73V, den lam viec voi cong suat 105W 3. Nguyen ly lam vice ciia bo chuyen doi cong suat RO LE CHUYEN MACH BO GIAM AP VA NAN DONG 10/72 Bg chuyen doi cong suat ban chat la rale hen gia, su dung nguon dien mot chieu. Bg dem thai gian dugc cai dat theo gicr Ih-2h-3h Khi dat dugc thai gian TRIAC khoi dgng kich hoat ra I e lam viec ' ^" " ' " ' Ra le a trang thai khong lam vice mach thuang dong giiip balat hoat dong a mirc cong suat cao. Khi co tac dgng ra le dong cong tac thuang ma, luc do balat lam viec a cong suat thap ; 4. Nguyen ly lam vice ciia bo khoi dong B 0- 0 La N 0- - Khi CO dien phan ap thanli 2 phan : Cl, C2 - Qua 2 dilt zener dua dien ap vao cue G cua triac - Triac ma xuit hien dien ap khoang 120 V a sa cap cua bien ap xung BAX - Diu thu cip dat dien ap 2,8 - 5 kV tiiy theo thiet ke. Trong nira chu ky duang ciia tin s6, khi den phong dien trong thai gian rat ngan liic do dien ap rai tren G =0, nhiem vu ciia bg khai dgng da hoan thanli. - Dong dien tilp tuc chay true tiep qua cugn thir cap. 11/72 [...]... nhiet ciia cugn day (m') Tinh chgn: Chgn KT = 14 W/m'.°C ST = 2( a,+b,)h+ (2a,+2b, +27 r*l)h+ 2( 2(a,+b,)l+ 7r.l') = 2( 21,5 + 93) .24 + (2. 21,5 + 2. 93 + 27 x 11,5) .24 + + 2( 2 (21 ,5+ 93).11,5 +71.11,5') = 18 824 ,11 (mm') = 0,018 82 m' Vay: At = 16,5/(14.0,018 82) = 62, 7 CQ Thoa man dilu kien cho phep d cap each nhiet B: At = 65 °C Nhiet do cue dai cho phep ciia cugn day d cap B la: Tw =130 °C 9 He so cong suat:... nhiet ciia cudn day (m') Tinh chgn: Chgn KT = 14 W/m'.°C ST = 2( a,+b|)h+ (2a,+2b| +27 r*l)h+ 2( 2(a,+bi)l + 7r.l') = 2( 21,5 + 93) .24 + (2. 21,5 + 2. 93 + 27 r.l 1,5) .24 + + 2( 2 (21 ,5+ 93).l 1,5 + 71.11,5') = 18 824 ,11 (mm') = 0,018 82 m' Vay: At =13,48/(14.0,018 82) = 51,16 C'C) Thoa man dieu kien cho phep d cap each nhiet B: At = 65 °C Nhiet do cue dai cho phep cua cudn day d cap B la: Tw =130 "C 9 He so cong suat:... ^C - ^! 1 2j 88-0 02 27/ 72 t Gia dau cuon day: Nhya PA Composite ^ 46-0. 02 ^ 34-0, 02 1 cni T J II 2KT5,5| I 1,5 2R1 "1 4KT1 I 2 R0,5 2KT4 Oil CO / 1.5 a in" I 2KT1,5 I n= l R0,5 nl 2R1,5 R1,5 _21 _ 34 10 , 5 i2; 34 (N O 1 t 2R1 1 L J ^ i i H -^i T 1 1 "i 8R0 ,2 C7)j "i1 1 36 1 De Balat: Thep CT3 100 I ' I ' 1,5 ^1 ^ • • i i-i r TTieo/ Ty l $2: 1 ol 10 1 su6tR2,5 6 4R2 (3 "LF ^ 4R1,5, 4R2 15 2 Id ren M3... 471.10- ^21 .10"l85.10"Vl.10"^ = 2, 24.10"^ (H) Gg| = 2( 0 ,26 .poa) +2( 0 ,26 .po-b) = 2( 0 ,26 .471.10" ^21 .10'^)+ 2( 0 ,26 .4:: 10-^.85.10-^) = 6,93.10"^ (H) Gg2 = 4.0,077.p„.5 = 4.0,077 471.10-^.1.10'^ = 3,87.10"'° (H) Gg3 = 2. 2.po(a+b)/(7r(5/m+l)) = 2. 2 47t.l0-^ (21 + 85).10-V(7i(l + 1/1,5) = 1,017.10'^ (H) V d i m = 1,55= 1,5.10'^ (mm) Gg4 = 4.po.m/4 = 4.47i.lO'\l,5.10"V4 = 1,88.10"'' (H) Vay: Gg = 2, 24.10"^ +... (s) Sai sd (%) 19 20 22 0.5 72 18781 -4.3 0.5 72 18781 -4.3 0.571 18737 -4.1 23 30 35 40 0.569 18693 -3.9 0.5 52 18 124 -0.7 0.540 17730 0.531 17 424 15 32 45 47 0. 527 1 729 3 0. 527 1 729 3 50 55 62 0. 529 17367 0.537 17643 0.547 17949 39 39 35 20 03 4 C=0,45^F Nhiet do (°C) Ciiu ky xung (s) Thdi gian (s) Sai sd (%) 30 0.549 18037 -0 .2 35 40 0. 523 17161 0.500 16417 47 88 45 0.484 158 92 11.7 48 50 55 60... tiet (01)f / I )( 02) • \ A {06 'l- y y 4 ^y-\ QO /\ \ 0(.N HPSS150/100 '- v* ijowf*'a**i „ u 0.' 0 « ~1\ Cow B > (H) -'''~~L B 0-1.1 t-V COw.Sijil 1? ^ c L2I^ 26 / 72 / \ i Can cir vao cac tinh toan tren trien khai thiet ke cac chi tiet cu the nhu sau: La thep chiT U: Thep s 221 2 122 116 115 2 Vdt 45° _2R1 R2,5 7_^ CM O 2R0,4 "nr-R.1 T 4^ i J00,8_ J26_ 130 La thep chu' T: Thep s 221 2 42 ^ •"I- 00 CD... V,, =H.L.b.0,97 -2. 1 l,5 .24 .b.0,97=45.65.85.0,97- 2. 11,5 .24 .85.0,97 = 195654(mm^) =>Gn,=195654.10"''.7,85.10"^ = 1,536 tkg) C h g n k = 1 ,28 B la mat do tir thdng ciia mach tir (T) B = I.W.Gg/Sg = 1, 82. 340 .2, 42. 10"V (21 .10"l85.10"^) = 0,838 (T) f la tan sd mach dien (Hz), f = 50 Hz Tra dugc pi/50 = 2, 5 W/kg Po = k.p,/5o.B'.(f750)P = 1 ,28 .2, 5.0,838' 1 = 2, 25 (W/kg) Vay: Ppe = Po-G^ = 2, 25.1,536 = 3,45... U/Ic = 22 0/1,03 = 21 3,195 (Q) Vay giii tri dien dung C = l/ (27 if.Zc) = 1/ (27 1.50 .21 3,195) = 14,94.10"^ (F) Chgn tu bii vdi dien dung C = 17pF Ket luan: Ket qua thiet ke tinh toan nhu sau: 1 Thong so mach tir: Vat lieu: Thep ky thuat dien s22l2 Sd la: 25 8 Chilu cao: H = 46 mm ; Be ngang: L = 65 mm Chieu dai: b = 85 mm , Cira sd : 11,5 mm x 24 ,5 mm Cue tir: a = 21 mm Gdng tir: 10,5 mm ( = l/2a) / H 24 11,5... (3 "LF ^ 4R1,5, 4R2 15 2 Id ren M3 -o (3- K: 90 16 9,5 2 1 KT26 6 ""1 a = r\= L?KT _43_ 48 168 28 / 72 ^\ S Tong hop cac chi tiet trong balat 2 cap cong suat TT 1 Cac chi liet va cum chi tiet La thep ciiuU 2 Ky hieu ban ve Vat lieu BL-HPS150/100-001 So lu'O'ng 165-1 S 221 2 La thep cliCr T BL-HPS150/100-0 02 165-1 822 12 3 Nap che BL-HPS 150/100-003 02 Nhua PC 4 De BL-HPS150/100-004 01 Thep CT3 5 Nhan san... day TCVN 02 Thep CT3 10 Cum cudn day BL-HPS 150/100-100 01 Day e may 11 Gia dau cudn day BL-HPS 150/100-101 02 12 Ldi each dien BL-HPS 150/100-1 02 02 Nhua PA composite Phip 13 Dau cdt BL-HPS 150/100-103 03 Ddng J1 62 14 Cum cue dau day BL-HPS 150/100 -20 0 01 15 Vd cue dau day BL-HPS 150/100 -20 1 01 Nhua PP 16 Ong chira day BL-HPS 150/100 -20 2 03 Gel thiiy tinh 17 Vit kep day TCVN 06 Ddng ;1 62 II .2 TRIEN . ST = 2( a,+b,)h+ (2a,+2b, +27 r*l)h+ 2( 2(a,+b,)l+ 7r.l') = 2( 21,5 + 93) .24 + (2. 21,5 + 2. 93 + 27 x. 11,5) .24 + + 2( 2 (21 ,5+ 93).11,5 +71.11,5') = 18 824 ,11 (mm') = 0,018 82 m' 471.10- ^21 .10"l85.10"Vl.10"^ = 2, 24.10"^ (H). Gg| = 2( 0 ,26 .poa) +2( 0 ,26 .po-b) = 2( 0 ,26 .471.10" ^21 .10'^)+ 2( 0 ,26 .4::. 10-^.85.10-^) = 6,93.10"^ (H). Gg2 . W /22 0 V dimg cho den TIO & T8 2. Balat sat tir 20 W /22 0 V diing cho denTlO & T8 Tiep tuc cong viec phan khai do, Cong ty VINAKIP trien khai bo dieu khien 2 muc cho den Natri cao